Interesting Camry Hybrid Front Brake Pad wear, or lack of wear

[Hugh R]

I had a flat yesterday, (nail) refilled the tire and drove a few miles to the Goodyear dealer where I bought my last tires (free flat fix and free rotation). He showed me some dampness around the top of the front struts and tried to sell me $500 in new struts (not today). Asked about my original front brake pads and we looked and he said they still had about 90% of their meat on them, after 90K miles!!

With a hybrid when you step on the brake pedal, it uses the electronics to take the braking action and recharge the hybrid batteries, which I knew. But 90% of brake pad meat after 90K miles is a lot more than I expected. My uncalibrated fingernail on the edge of the front discs tells me they only have a few thou. of wear. Didn't think to check the rears pads while it was on the rack, but the rear discs have similar wear. I'm guessing that only the fronts participate in the dynamic braking and that the rears are just along for the ride. I guess its possible that my rear pad could wear out before my fronts.

Just thought this was interesting.

[cockerpunk]

most modern cars also have a heavy rear brake bias. its mostly for brake tappers.

[Hugh R]

Really? I wouldn't have guessed that since physics says 70% of breaking force is in the front.

I know if I lock up the brakes on my Targa the rt. rear locks up first. Rear engine, throw out the anchor, driver only scenario I guess.

[jyl]

No brake work on our Prius until >100K miles.

[Flieger]

The rear brake bias is incorrect. They will have a heavy front bias but maybe not as heavy as they would without ABS. There will likely be a proportioning valve to allow a knee in the bias curve so that when there is less pressure applied (less deceleration, less weight transfer) the bias is less forward than when you really stomp the pedal. This is to make better use of the rear brakes when on a low friction surface, when the bias doesn't match the weight transfer.

[cockerpunk]

Originally Posted by Flieger

The rear brake bias is incorrect. They will have a heavy front bias but maybe not as heavy as they would without ABS. There will likely be a proportioning valve to allow a knee in the bias curve so that when there is less pressure applied (less deceleration, less weight transfer) the bias is less forward than when you really stomp the pedal. This is to make better use of the rear brakes when on a low friction surface, when the bias doesn't match the weight transfer.

yup

at low braking pressures, modern cars will only use there rear brakes basically.

only under full braking pressure, will the front bias appear.

[Hugh R]

My 1930 Rudge Whitworth motorcycle has something sort of similar. You pull the handle bar brake lever it operates the front brake only. You use the foot brake and it pulls in the front and rear brakes. For 1930 technology, you "bias" it by adjusting the brake shoe to drum clearances for road riding or racing with cable adjustments.

[Flieger]

Originally Posted by cockerpunk

yup

at low braking pressures, modern cars will only use there rear brakes basically.

only under full braking pressure, will the front bias appear.

I think you'll find the fronts are always doing most of the work. You never want the rears to lock first, and most cars today have a front weight bias to begin with, so the front has the most grip.

I can't think of any cars meant for use on pavement that have a rear brake bias, apart from some go-karts with a solid rear axle.

[95avblm3]

Originally Posted by Flieger

I think you'll find the fronts are always doing most of the work. You never want the rears to lock first, and most cars today have a front weight bias to begin with, so the front has the most grip.

I can't think of any cars meant for use on pavement that have a rear brake bias, apart from some go-karts with a solid rear axle.

My wife had an '07 Volvo S40 that wore the rear pads out first... Changed them around ~60k miles. Never had to do the fronts... It was totaled at about 99k miles. I was always baffled by the rear pad wear in that front-wheel drive car. I guess this rear-bias discussion could explain it... and with ABS, no lockup.

[mattdavis11]

2007 Prius, a company car, driven as hard as I could drive it. Somewhere along the way I thought it would be a wise idea to change the pads, it had 175K. They had to be due. Nope, not even close, back to the store the pads go.

It had over 200K, and the brakes were perfect the entire time. I don't wear out brakes on my own vehicles, but those pads should have been worn out.

[Tobra]

CP, where do you get this stuff?

I think your analysis is right on, Mr R

[mattdavis11]

I know CP is wrong on the Prius, the fronts lock and you lose steering until the ABS catches up with the input from the driver. I looked into how to disable the ABS, but couldn't be steered in the right direction and got nowhere.

I can't imagine another vehicle made by the same manufacturer being different.

[Oracle]

When I had the Dodge Caravan was the same...
Replaced rears like 2:1 or 3:1 of front pads.

Quote de Flieger

I think you'll find the fronts are always doing most of the work. You never want the rears to lock first, and most cars today have a front weight bias to begin with, so the front has the most grip.



I can't think of any cars meant for use on pavement that have a rear brake bias, apart from some go-karts with a solid rear axle.

My wife had an '07 Volvo S40 that wore the rear pads out first... Changed them around ~60k miles. Never had to do the fronts... It was totaled at about 99k miles. I was always baffled by the rear pad wear in that front-wheel drive car. I guess this rear-bias discussion could explain it... and with ABS, no lockup.

[Flieger]

Rear brakes are often different size from the front (much smaller). Sometimes they are even drums. That will affect how long pads last.

If it happens on sports cars it is the traction control working (you will usually see weird wear patterns on the rotors, particularly if they are cross-drilled).

[chapo]

My 06 f250 and 2012 f150 both use up the rear pads way before the front. I chalked it up to abs. The brakes are not really any smaller on the rear

[aigel]

I hardly touched the pads on my TDI at 50k. No doubt they will go way beyond 100k. I drive looking ahead and use the engine to slow me down (stick). On automatic cars, I find the brake wear is definitely a lot heavier.

G

[speeder]

I remember back in the '80s when I worked at the Porsche/Audi dealer, the service manager told me that there were certain cars that never wore out the rear brakes. They were all FWD Audis with all the weight over the front wheels and nothing in back but a couple wheels along for the ride.

When I asked what he meant by, "never", he said, "never". 150k mile cars with original rear brakes, still not worn out.

Most good cars have well-proportioned braking systems and bias things in such a way that the fronts and rears should wear fairly evenly. Obviously, the fronts are doing more work but the size of the brakes F/R and proportioning system allows for maximum/even braking using all four paws.

[oldE]

Hugh,

Interesting how the regenerative braking is reducing the wear and tear on the other system. I suspect it will vary among drivers as well, taking into account different driving styles.

In my experience, premature rear pad wear is a sign that the rear brakes are not getting exercised and begin to stick and drag. We saw this on my wife's MR2. She did not drive it hard at all and the calipers seized in a couple of years (daily driver in the salt-covered roads in winter).

Best
Les

[fingpilot]

Hugh;

My '04 Prius has 170k. Original pads and shoes. Front pads are 79% of original thickness. Rear shoes were dusty and perhaps 20% consumed. Panic stops I hear the rears in anti-skid.

Not unusual wear for regen braking.

[speeder]

So much for my business plan of doing brake jobs on the 8 million Priuses in this town.